We propose to continue our picosecond resonance Raman studies of visual pigments. The overall aim of the research is to elucidate the conformational dynamics of rod and cone photoreceptor proteins and gain a deeper understanding of the molecular basis of vision. We have built a picosecond resonance Raman instrument that photolyzes and probes a sample of visual pigment with a 30 psec laser pulse at 532 nm. Spectra obtained with this apparatus have revealed that the 11-cis retinal group of rhodopsin isomerizes to a distorted all-trans form within 30 psec of the absorption of a photon. Our goal now is to improve the time resolution and complete the construction of a two-pulse time-resolved picosecond resonance Raman instrument. This apparatus will be used to elucidate the molecular dynamics of photolyzed rhodopsin starting at times of a few picoseconds. Low-temperature picosecond studies will be carried out to measure the Raman spectrum of an intermediate before bathorhodopsin. The spectral range of our apparatus will be extended to the ultraviolet region to enable us to monitor some of the earliest conformational changes in the protein as expressed in the resonance Raman spectra of aromatic side chains. Chicken iodopsin will be studied in addition to bovine rhodopsin. These resonance Raman studies are designed to provide insight into fundamental questions such as: (1) How does the protein component of visual pigments tune the absorption maximum of its retinal chromophore? (2) How does the protein enhance the photosensitivity and channel the photochemistry of its bound retinal? (3) What are the critical light-induced conformational changes in the protein that trigger visual excitation?